This invention relates to a square root circuit such as those used with differential pressure transducers in the measurement of flow. The purpose of such a circuit is to provide a signal which is a directly related to flow when the primary measuring element produces a signal directly related to the square of the flow, such as would be derived from a differential pressure transducer.
In the prior art, analog circuits for this purpose have been constructed using high gain amplifiers with a squaring circuit inserted in the negative feedback path, as described in my U.S. Pat. No. 4,506,174, issued Mar. 19, 1985. That prior art circuit is a true insertion circuits in that it can be directly inserted into another circuit without changing the voltage levels or power requirements of that other circuit. It is desirable to provide a circuit of that type which would be cheaper to construct and which would provide improved conformity to the desired square root characteristic. It is therefore an object of this invention to provide an improved square root circuit which draws little power and which works at the typical voltage levels of circuits in which it might be inserted. It is also an object of this invention to provide such a circuit with sufficient quality to assure square root conformity to within .+-.0.1% from full range to 4% of input with good conformity to as low as 1% of input and to do so at a low cost while avoiding susceptibility to erratic operation in the region near zero.